A disk drive system includes one or more magnetic recording disks and control mechanisms for storing data on the disks. The disks are constructed of a substrate, that may be textured, and multiple film layers. In most systems, an aluminum-based substrate is used. However, alternative substrate materials such as glass have various performance benefits such that it may be desirable to use a glass substrate. One of the film layers on a disk is a magnetic layer used to store data. The reading and writing of data is accomplished by flying a read-write head over the disk to alter the properties of the disk's magnetic layer. The read-write head is typically a part of or affixed to a larger body that flies over the disk, referred to as a slider.
The trend in the design of magnetic hard disk drives is to increase the recording density of a disk drive system. Recording density is a measure of the amount of data that may be stored in a given area of a disk. To increase recording density, for example, head technology has migrated from ferrite heads to film heads and later to magneto-resistive (MR) heads and giant magneto-resistive (GMR) heads.
Achieving higher areal density (i.e., the number of stored bits per unit surface area) requires that the data tracks be close to each other. Also, because the track widths are very small, any misregistration of a track (e.g., thermal expansion) may affect the writing and/or reading with the head by an adjacent track. This behavior is commonly referred to as adjacent track interference (ATI). One method for addressing ATI is to pattern the surface of the disk to form discrete data tracks, referred to as discrete track recording (DTR). DTR disks typically have a series of concentric raised zones (also known as hills, lands, elevations, etc.) for storing data and recessed zones (also known as troughs, valleys, grooves, etc.) that provide inter-track isolation to reduce noise. By putting voids between tracks, reading and/or writing by a head may be accomplished more easily. Such recessed zones may also store servo information. The recessed zones separate the raised zones from one another to inhibit or prevent the unintended storage of data in the recessed zones.
One problem with prior DTR magnetic recording disks is that they may not have a desired “preferred” circumferential orientation of magnetic material in their magnetic recording films. “Preferred” circumferential orientation of the magnetic media aids in achieving optimal signal-to-noise ratio (SNR) and resolution to obtain the best possible performance from the magnetic media.